content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.observable.internal.operators;
  
  import java.util.concurrent.atomic.*;
  
  import io.reactivex.common.*;
  import io.reactivex.common.exceptions.*;
  import io.reactivex.common.internal.disposables.DisposableHelper;
  import io.reactivex.observable.*;
  import io.reactivex.observable.extensions.*;
  import io.reactivex.observable.internal.queues.*;
  
  public final class CompletableConcat extends Completable {
      final ObservableSource<? extends CompletableSource> sources;
      final int prefetch;
  
      public CompletableConcat(ObservableSource<? extends CompletableSource> sources, int prefetch) {
          this.sources = sources;
          this.prefetch = prefetch;
      }
  
      @Override
      public void subscribeActual(CompletableObserver s) {
          sources.subscribe(new CompletableConcatObserver(s, prefetch));
      }
  
      static final class CompletableConcatObserver
      extends AtomicInteger
      implements Observer<CompletableSource>, Disposable {
          private static final long serialVersionUID = 9032184911934499404L;
  
          final CompletableObserver actual;
  
          final int prefetch;
  
          final ConcatInnerObserver inner;
  
          final AtomicBoolean once;
  
          int sourceFused;
  
          int consumed;
  
          SimpleQueue<CompletableSource> queue;
  
          Disposable s;
  
          volatile boolean done;
  
          volatile boolean active;
  
          CompletableConcatObserver(CompletableObserver actual, int prefetch) {
              this.actual = actual;
              this.prefetch = prefetch;
              this.inner = new ConcatInnerObserver(this);
              this.once = new AtomicBoolean();
          }
  
          @Override
          public void onSubscribe(Disposable s) {
              if (DisposableHelper.validate(this.s, s)) {
                  this.s = s;
  
                  if (s instanceof QueueDisposable) {
                      @SuppressWarnings("unchecked")
                      QueueDisposable<CompletableSource> qs = (QueueDisposable<CompletableSource>) s;
  
                      int m = qs.requestFusion(QueueDisposable.ANY);
  
                      if (m == QueueDisposable.SYNC) {
                          sourceFused = m;
                          queue = qs;
                          done = true;
                          actual.onSubscribe(this);
                          drain();
                          return;
                      }
                      if (m == QueueDisposable.ASYNC) {
                          sourceFused = m;
                          queue = qs;
                          actual.onSubscribe(this);
                          return;
                      }
                  }
  
                  if (prefetch == Integer.MAX_VALUE) {
                      queue = new SpscLinkedArrayQueue<CompletableSource>(Observable.bufferSize());
                  } else {
                      queue = new SpscArrayQueue<CompletableSource>(prefetch);
                  }
  
                  actual.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(CompletableSource t) {
              if (sourceFused == QueueDisposable.NONE) {
                  if (!queue.offer(t)) {
                      onError(new MissingBackpressureException());
                      return;
                  }
              }
              drain();
          }
  
          @Override
          public void onError(Throwable t) {
              if (once.compareAndSet(false, true)) {
                  DisposableHelper.dispose(inner);
                  actual.onError(t);
              } else {
                  RxJavaCommonPlugins.onError(t);
              }
          }
  
          @Override
          public void onComplete() {
              done = true;
              drain();
          }
  
          @Override
          public void dispose() {
              s.dispose();
              DisposableHelper.dispose(inner);
          }
  
          @Override
          public boolean isDisposed() {
              return DisposableHelper.isDisposed(inner.get());
          }
  
          void drain() {
              if (getAndIncrement() != 0) {
                  return;
              }
  
              for (;;) {
                  if (isDisposed()) {
                      return;
                  }
  
                  if (!active) {
  
                      boolean d = done;
  
                      CompletableSource cs;
  
                      try {
                          cs = queue.poll();
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          innerError(ex);
                          return;
                      }
  
                      boolean empty = cs == null;
  
                      if (d && empty) {
                          if (once.compareAndSet(false, true)) {
                              actual.onComplete();
                          }
                          return;
                      }
  
                      if (!empty) {
                          active = true;
                          cs.subscribe(inner);
                      }
                  }
  
                  if (decrementAndGet() == 0) {
                      break;
                  }
              }
          }
  
          void innerError(Throwable e) {
              if (once.compareAndSet(false, true)) {
                  s.dispose();
                  actual.onError(e);
              } else {
                  RxJavaCommonPlugins.onError(e);
              }
          }
  
          void innerComplete() {
              active = false;
              drain();
          }
  
          static final class ConcatInnerObserver extends AtomicReference<Disposable> implements CompletableObserver {
              private static final long serialVersionUID = -5454794857847146511L;
  
              final CompletableConcatObserver parent;
  
              ConcatInnerObserver(CompletableConcatObserver parent) {
                  this.parent = parent;
              }
  
              @Override
              public void onSubscribe(Disposable d) {
                  DisposableHelper.replace(this, d);
              }
  
              @Override
              public void onError(Throwable e) {
                  parent.innerError(e);
              }
  
              @Override
              public void onComplete() {
                  parent.innerComplete();
              }
          }
      }
  }
  